Split ends closure device

ABSTRACT

A device closes a patent foramen ovale (PFO), thus reducing or eliminating blood flow through the defect. The device is formed from a tubular structure having split ends, such that, after insertion, struts defined by the split ends pivot in a radial direction away from the tube, thereby securing the device within the septal defect.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application60/561,544, filed Apr. 9, 2004, the entire contents of which areincorporated herein by reference.

BACKGROUND OF THE INVENTION

The invention relates to devices and methods for closing defects such asa patent foramen ovale (PFO).

A PFO is a persistent, one-way, usually flap-like opening in the wallbetween the right atrium and left atrium of the heart. Since left atrial(LA) pressure is normally higher than right atrial (RA) pressure, theflap typically stays closed. Under certain conditions, however, RApressure can exceed LA pressure, creating the possibility for right toleft shunting that can allow blood clots to enter the systemiccirculation.

In utero, the foramen ovale serves as a physiologic conduit forright-to-left shunting. After birth, with the establishment of pulmonarycirculation, the increased left atrial blood flow and pressure resultsin functional closure of the foramen ovale. This closure is typicallyfollowed by anatomical closure of the two over-lapping layers of tissue,septum primum and septum secundum. However, a PFO has been shown topersist in a significant minority of adults.

The presence of a PFO has no therapeutic consequence in otherwisehealthy adults, however, patients suffering a stroke or TIA in thepresence of a PFO and without another cause of ischemic stroke areconsidered for prophylactic medical therapy to reduce the risk of arecurrent embolic event. These patients can be treated with oralanticoagulants, but such drugs have the potential for adverse sideeffects such as hemorrhaging, hematoma, and interactions with otherdrugs. In certain cases, such as when the use of anticoagulation drugsis contraindicated, surgery may be used to suture a PFO closed. Suturinga PFO requires attachment of septum secundum to septum primum with astitch (continuous or interrupted), which is the common way a surgeonshuts the PFO under direct visualization.

Non-surgical closure of PFOs has become possible with umbrella devicesand a variety of other similar mechanical closure designs developedinitially for percutaneous closure of atrial septal defects (ASD). Thesedevices allow patients to avoid the potential side effects oftenassociated with anticoagulation therapies.

SUMMARY OF THE INVENTION

Embodiments of the invention include devices and methods for closing aseptal defect, including a PFO. In one embodiment, the device includes atubular structure having dimensions suitable for insertion into acatheter, and slits extending from one or both ends that define strutsthat can pivot away from the rest of the tube to provide desirableanchoring of the device within a septal defect. The slits can be spacedat regular or irregular intervals along the tube circumference, and canhave different lengths. A slit extending from one end of the tube can bealigned or offset with respect to a corresponding slit extending fromthe other end. The configuration of slits can be designed to optimizethe distribution of clamping forces provided by the struts defined bythe slits. In some embodiments, prior to insertion into the body, strutsdefined by slits from one end can overlap or touch corresponding strutsdefined by slits from the other end. The device can further include arecovery wire attached to one or more struts, such that tension appliedto the recovery wire can enable the device to be retracted into thecatheter.

The device is preferably made from a polymer with shape memoryproperties, and can also include a means for causing the struts toextend radially when released from the catheter into the body. The meanscan include a tissue scaffold attached to at least one of the struts,and/or a tensioner, such as an elastic band or string. The tissuescaffold can be made of a bioresorbable material, a flexiblebiocompatible material capable of promoting tissue growth, a polyesterfabric, a Teflon-based material, a polyurethane, a metallic mesh,polyvinyl alcohol, an extracellular matrix, a synthetic bioabsorbablepolymeric scaffold, collagen, and combinations thereof. At an axiallycentral portion, the device can further include whiskers to provoke aninflammatory response, a collar including a sponge-like material, a drugcoating, or an anticoagulant.

Benefits of certain embodiments can include atraumatic shape, goodconformity to the anatomy (especially when used for a PFO), smalldiameter delivery sheath, no permanent foreign material, ease ofmanufacturing, cost effectiveness, and overall simplicity. Otherfeatures and advantages will become apparent from the following detaileddescription and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a tube with slits used to form a closuredevice.

FIG. 2 is a perspective view of the tube of FIG. 1 with the ends shownsplit extending outwardly.

FIGS. 3 and 4 are a perspective view and front elevational view,respectively, of an embodiment with three struts and whiskers and/orsponge material.

FIGS. 5 and 6 are side and front (through line 6-6 of FIG. 5) views ofthe device of FIGS. 3 and 4, shown positioned in the PFO.

FIG. 7 is a perspective view of an alternative embodiment to FIG. 3 witha tissue scaffold.

FIGS. 8 and 9 are further embodiments of a closure device, and

FIGS. 10 and 11 are perspective views of the device of FIG. 8 with theaddition of a connector and shown in vivo.

FIGS. 12-16 are views of another embodiment of the present invention.

FIGS. 17-23 are views of another embodiment shown with and without atissue scaffold.

DETAILED DESCRIPTION

The present invention includes embodiments of a closure device for aPFO, atrial septal defect (ASD), or other suitable defect, preferablyformed from a single tube with cuts made to produce the final deviceshape. The device can have struts that extend radially outwardly from acentral portion, or loops that extend from the central portion and backto the central portion, preferably in a plane that is parallel to thedefect (such as the PFO tunnel).

Referring to FIG. 1, in one embodiment a closure device is made from asingle polymer tube 10 by providing slits 12, 14 at both ends andsetting a desired shape, such as by thermo-mechanical treatment, toproduce a design as shown in FIG. 2. This treatment can include heatingor other thermal steps, and mechanical steps, such as folding back thestruts.

This device has a first set of struts 16 a, 16 b and a second set ofstruts 18 a, 18 b at the opposite end. A center portion 20 is betweenthe ends and typically has no cuts. As shown in FIG. 2, a recovery wire22 and lug 24 can optionally be provided at a proximal end (right atriumin case of use for a PFO) and coupled to struts 16 a, 16 b. The devicecan be collapsed and loaded into a delivery sheath by grabbing the lugand bringing the split ends on a proximal side back together.

The device is formed back into a tube for deployment via a catheter.Upon deployment, the occluder reverts to its designed shape due toelastic recovery of the polymer, shape memory recovery, or/and the useof strings, springs, or elastic sheet (tensile elements). Even thoughtensile elements may be thinner than the frame, they can produce muchhigher forces than the frame itself, thus assisting the frame in itsrecovery. This is possible because the primary mode of deformation is intension, while the frame deformation mode is in bending and torsion.Tensile elements also provide a way for centering so the occluder can bepositioned properly in a wide defect.

Without a wire and a lug or other method to grab the struts at theproximal end, if the proximal end needed to be withdrawn back into acatheter, the struts would fold over the outside of the central portion,thereby increasing the cross-sectional profile. This may be acceptable,but a smaller profile would be obtained by pulling the ends of thestruts back into the tubular shape. At the distal end where struts 18 a,18 b are (the left atrial end in case of use in a PFO), a pulling actionof the device back into a catheter would naturally urge the struts backinto the tubular configuration.

The number of radially extending parts (struts) formed from each end ofa tube could be greater than two, such as any number from 3 to 10. Usingmany more struts, such as more than 10, may be possible but could beimpractical because there could be a considerable decrease in theirstiffness due to the decrease in thickness. More struts at each end maybe possible with appropriate materials.

FIGS. 3 and 4 show a closure device 30 with 3 slits made at each end ofa tube to form three struts 32 a-32 c, 34 a-34 c at each end of thetube. Small strips, referred to here as whiskers 36, made of the samematerial as the tube or some other materials can be attached to thecentral portion 38, or material can be partially shaved from the centerregion 38 of the tube. These whiskers can produce an inflammatoryresponse and speed up the healing process. The whiskers can have a drugcoating, such as with an anti-coagulant, or can be made of a drug thatis slowly dissolved. Rather than the whiskers as shown, a collar with afoam or sponge-like material, such as polyvinyl alcohol, can be used,and can include an anti-coagulant.

FIGS. 5 and 6 show the embodiment of FIGS. 3 and 4 as deployed in a PFOtunnel. As indicated here, struts 32 a and 34 a have ends that contactseptum primum 50, and struts 32 b and 34 b have ends that contact septumsecundum 52. Struts 32 c and 34 c are not shown in FIG. 5, but asindicated in FIG. 6, they could be positioned against septum primum orseptum secundum. These struts cooperate to provide a compressiveclamping force to the PFO.

Center portion 38 can extend through the PFO tunnel and can be at anacute angle A relative to a downward vertical direction. This is anexample of how the configuration can conform well to the anatomy.

As shown in top view FIG. 4, the struts can be formed so that they areevenly distributed circumferentially. Generally, the struts can beequally spaced by 360°/n in the circumferential direction, where n isthe number of struts; for 3 struts, each strut is at 120° relative toadjacent struts. The struts at one end can be offset by (360°/n)/2 fromthe struts at the other end.

Such an even distribution at each end and equal offset of the two endsrelative to each other can be used, but such relationships are notrequired. The slits at each end of the tube can be formed in one of anumber of different ways, and can produce struts that have differentwidths. In addition, while the slits may be rather narrow as shown, suchthat the sum of the widths of the struts is just a little less than thecircumference of the tube, the slits can be made wider so that thestruts are narrower, although it is generally preferable to have widerstruts to provide good support.

FIG. 7 is a perspective view of a device similar to that of FIGS. 3 and4, but with the addition of a tissue scaffold. While preferablybioresorbable, the tissue scaffold may be formed of any flexible,biocompatible material capable of promoting tissue growth, including butnot limited to polyester fabrics, Teflon-based materials such as ePTFE,polyurethanes, metallic meshes, polyvinyl alcohol (PVA), extracellularmatrix (ECM), or other bioengineered material, synthetic bioabsorbablepolymeric scaffolds, other natural materials (e.g. collagen), orcombinations of the foregoing materials. Also, a tissue scaffold may beformed of a thin metallic film or foil. The scaffold may be attached toone or both sides of the device. The tissue scaffold or the frame canhave drugs or biological agents to accelerate the defect healing processand/or decrease thrombosis.

Referring to FIG. 8, in another embodiment, the tube has four slits ateach end to produce four struts at each end of the tube. As indicatedabove, whiskers and/or sponge material and tissue scaffolds could beadded, as could a recovery wire and lug.

Referring to FIG. 9, an embodiment similar to that of FIG. 8 is shownwith the addition of elastic bands or strings 90, 92 extending from endsof struts at one end to ends of struts at another end. These bands canbe provided for some or all of the opposing struts. As shown here, thestruts can be located at the same circumferential position at each end(and not offset, unlike in FIG. 4). The strings help to bend back thestruts, and can also help to orient and center the device as shownbelow.

In the embodiments of FIGS. 10 and 11, device 100 has four struts ateach end. From each of two of the struts, an elastic band 102, 104extends from one strut to a corresponding strut at the opposite end ofthe device. The bands can provide centering and/or be inflammatory.

FIGS. 12-15 show another embodiment. Referring specifically to FIG. 12,the tube has several different slits, including two longer slits, 180°apart, at each end to form bases 120 and 122 for struts, and two shorterslits are made, offset by 90° from the longer slits, to form struts 124,126, 128, and 130 at one end. As also shown in FIGS. 13 and 14, struts124-130 can be formed at one end to be offset at a circumferential angleof 90° with respect to struts at the other end, identified here asstruts 132, 134, 136, and 138.

Referring to FIG. 15, in this side view, it is shown that the struts canbe formed during manufacture such that the ends of the struts atopposite ends overlap when treated and before deployment. In otherwords, a distal end strut 126 and a proximal end strut 136 cross suchthat the end of strut 126 is closer to the proximal end than the end ofproximal strut 136.

This configuration may be more suitable for a polymer embodiment or foranother type of material that may not have full recovery force. Nitinol,for example, has rather high recovery force and is better able toreassume its original shape after being folded into a catheter and thendeployed. A polymer may not have quite as much recovery force, andtherefore it can be useful to compensate partially for this by allowingstruts at one end to cross the struts at the other end in themanufactured configuration. The struts will be contacting tissue thatseparates them, and therefore in the deployed position, the struts willbe spaced part and not overlap.

Referring to FIG. 16, the tube in this case is shown with slits that aresomewhat similar to that in FIG. 12, except that rather than the longslits being offset as in FIG. 12, the long slits in FIG. 16 at oppositeends are circumferentially aligned. In this embodiment, struts 162, 164,166 and 168 are produced at one end, with similar struts at the otherend. Unlike the embodiment as shown in FIG. 13, in which struts 124 and128 extend substantially parallel, struts 162 and 166 are curved to cometogether at an end 170. Other struts are matched up pairwise in asimilar manner, forming in effect four loops.

Each of these loops is preferably parallel to the defect. This allowsmost of the loop to be in contact with the tissue, such as one of thesepta in the case of a PFO. The loop can be perpendicular to the defect,which is more like a strut that doubles back to the central portion.This configuration is possible but less desirable.

As shown in FIG. 19, the ends 170, 172 of these loops can be formed tobe very close together or even touch when manufactured. As describedabove, a material with a recovery that does not fully come back intoplace may be compensated by bringing the ends together or overlapping asdescribed above.

FIG. 20 shows still another embodiment. As shown here, shorter andlonger axial slits are not that much different, thereby producing largerloops when ends of the struts are brought together as shown in FIGS. 21and 22 to create loops in a manner similar to that shown in FIG. 17. Inthis case, a tissue scaffold can also be provided in advance and duringmanufacture to the loops to result in the scaffold on the device asshown in FIGS. 21 and 22.

As indicated, the slits can have different widths, different numbers,and different slits can be formed with different lengths. In the case ofstruts, the ends of the struts contact the tissue, while in the case ofthe loops, as shown in FIGS. 17 and 21, for example, the loop maycontact the tissue over a larger area, thereby producing less trauma tothe patient. To reduce trauma with struts, ends of the struts can bemodified, such as rounded to reduce trauma that may be provided toseptum primum and septum secundum when implanted.

The proximal and distal end loops in FIG. 17 are aligned, but they couldbe rotationally offset, preferably by 90 degrees so the ends areperpendicular to each other. This can be accomplished by changing thepattern of slits in a tube.

As indicated before, the device can be deployed through a catheter usinggenerally conventionally known processes. This description relates tothe use for a PFO, where the proximal side is the right atrium and thedistal side is the left atrium, but the process could be used for othertypes of defects or treatments.

The occluder in its manufactured form is essentially folded back intothe tubular form and inserted into a catheter. The distal end of thecatheter is inserted into the left atrium where the catheter and theoccluder are moved relative to each other so that the struts, loops, orother radial pieces can fan out to contact septum primum and septumsecundum. This movement can be accomplished by pushing the occluder outof the catheter or retracting the catheter so that the occluder is notconstrained and can fan out. At this stage, it should not be difficultto pull the device back into the catheter if necessary to remove orreposition, as the radial pieces will tend to go back into the catheter.

When positioning at the distal end is satisfactory, the catheter isretracted through the PFO tunnel between septum primum and septumsecundum to expose the central portion, and is then moved further in theproximal direction to the device so that the catheter ceases toconstrain the radial pieces from fanning out in the right atrium. Asindicated above in FIG. 2, a recovery lug can be provided so that if thedevice is positioned and it is desirable to retrieve it, hooks or armscan be used to grab the lug to pull the proximal end in the right atriumback into a tubular configuration. Further distal direction movement ofthe catheter relative to the device will cause the distal (left atrium)end to be drawn back into the catheter.

As indicated before, the device can be made of nitinol or some othermetal with good recovery or shape memory properties, or it can be madeof a polymer. In the case of a polymer, the polymer is preferablytreated to make it make it radiopaque so that it can be seen on x-ray orother imaging equipment.

The shape and construction of such devices can have some advantages overother PFO closure devices. It has atraumatic shape, good embolizationresistance in some embodiments, and the ability to conform to theanatomy, especially in a defect tunnel due to the angled joint betweenthe proximal and distal side. The device can be repositioned or/andremoved during delivery. It has a small profile after deployment. It canbe made of bioresorbable components. Certain embodiments can be used toclose symmetric defects (e.g., atrial septal defects) or asymmetricdefects (e.g., PFO) using two versions of the device, i.e., one with astraight center tube and one with an angled center tube.

Occluders as described herein can be used with anti-thrombogeniccompounds, including but not limited to heparin and peptides, to reducethrombogenicity of the occluder and/or to enhance the healing responseof the septal tissue following deployment of the occluder in vivo.Similarly, the occluders described herein may be used to deliver otherdrugs or pharmaceutical agents (e.g., growth factors, peptides, orcells). The anti-thrombogenic compounds, drugs, and/or pharmaceuticalagents may be included in the occluders of the present invention inseveral ways, including by incorporation into the tissue scaffold, aspreviously described, or as a coating, e.g. a polymeric coating, on thetube(s) forming the distal side and proximal side of the occluder.Furthermore, the occluders described herein may include cells that havebeen seeded within the tissue scaffold or coated upon the tube(s)forming the distal side and proximal side of the occluder.

In some of the embodiments, such as that of FIG. 1, the occluder can beunitary or even monolithic (except for coatings or other surfacetreatments).

Having described preferred embodiments of the invention, it should beapparent that various modifications may be made without departing fromthe spirit and scope of the invention. While the device can be made froman extruded tube, pieces of polymer or other material can also be usedto make the device by applying different joining methods such aswelding, gluing, etc. The strands may have circular or polygonalcross-sections. The device can also be molded. The tube cross-sectionmay be circular or polygonal (including square and rectangular). Whilein most cases, each end has the same number of slits or loops, eitheraligned or offset, each end can be formed differently; e.g., one endcould have a different number or configuration of struts.

1. A device for use with a septal defect comprising a firstconfiguration having dimensions suitable for insertion into a catheter,the device in the first configuration including a tubular structure witha central axis, a proximal end, and a distal end, wherein at least oneof the ends has a plurality of slits extending in an axial directionaway from the end, the slits defining struts that are pivotable awayfrom the rest of the tubular structure.
 2. The device of claim 1,wherein the plurality of slits is selected from the group consisting of2, 3, 4, 5, 6, 7, 8, 9, and 10 slits.
 3. The device of claim 1, whereinthe plurality of slits have different lengths.
 4. The device of claim 1,wherein the slits are distributed evenly around the circumference. 5.The device of claim 1, wherein the slits are distributed unevenly aroundthe circumference.
 6. The device of claim 1, wherein the proximal anddistal ends each have slits, wherein each slit extending from theproximal end is aligned with a corresponding slit extending from thedistal end.
 7. The device of claim 1, wherein the proximal and distalends each have slits, wherein each slit extending from the proximal endis offset at a circumferential angle of less than 180 degrees withrespect to a corresponding slit from the distal end.
 8. The device ofclaim 1, wherein an axially central portion of the structure haswhiskers that provoke an inflammatory response.
 9. The device of claim1, further comprising a collar including a sponge-like material at anaxially central portion of the structure.
 10. The device of claim 1,further comprising a drug coating at an axially central portion of thestructure.
 11. The device of claim 1, further comprising ananticoagulant at an axially central portion of the structure.
 12. Thedevice of claim 1 further comprising means for causing the struts toextend radially away from the central axis of the tubular structure in asecond configuration when released from a catheter and into the body.13. The device of claim 12, wherein the means includes a tissue scaffoldattached to at least one of the struts.
 14. The device of claim 13,wherein the tissue scaffold includes at least one of a bioresorbablematerial, a flexible biocompatible material capable of promoting tissuegrowth, a polyester fabric, a Teflon-based material, a polyurethane, ametallic mesh, polyvinyl alcohol, an extracellular matrix, a syntheticbioabsorbable polymeric scaffold, and collagen.
 15. The device of claim12, wherein the means includes a tensioner comprising at least one of anelastic band and a string, the tensioner attached at one end to a strutextending from the distal end of the tubular structure and at the otherend to an opposing strut extending from the proximal end of the tubularstructure.
 16. The device of claim 12, wherein the structure comprises apolymer with shape memory properties.
 17. The device of claim 12,wherein the second configuration is suitable for blocking part or all ofa patent foramen ovale (PFO) and the struts secure the device within thePFO.
 18. The device of claim 12, wherein prior to insertion into thebody, the second configuration comprises distal end struts having endsthat are closer to the proximal end of the structure than the ends ofthe proximal end struts.
 19. The device of claim 12, wherein the secondconfiguration comprises at least one pair of distal end struts that arecurved so as to touch in a region near the end of each member of thepair, and at least one pair of proximal end struts that are curved so asto touch in a region near the end of each member of the pair.
 20. Thedevice of claim 12, further comprising a recovery wire attached to aplurality of struts, such that a tension applied to the recovery wirecauses the second configuration to deform in a manner that permits thedevice to be retracted into the catheter.
 21. A PFO closure devicecomprising a tubular structure having a central axis, a proximal end,and a distal end, wherein at least one of the ends has a plurality ofslits extending in an axial direction from the end, the slits definingstruts that extend radially away from the central axis of the tubularstructure, the struts securing the device within a tunnel of the PFO.22. The device of claim 21, wherein each proximal end strut iscircumferentially aligned with a corresponding distal end strut.
 23. Thedevice of claim 21, wherein at least one proximal end strut iscircumferentially offset with respect to a corresponding distal endstrut.
 24. The device of claim 21 further comprising a tissue scaffoldattached to at least one of the struts.
 25. A method for closing a PFO,the method comprising: inserting a tubular structure into the PFO via acatheter, the tubular device having a central axis, a proximal end, anda distal end, wherein at least one of the ends has a plurality of slitsextending in an axial direction from the end, the slits defining struts;causing the struts to extend radially away from the central axis suchthat the struts secure a central portion of the tubular structure withina tunnel of the PFO; and closing the PFO.
 26. The method of claim 25,wherein the tubular structure comprises a material selected from thegroup consisting of a polymer, a metal with shape memory properties, anda metal with elastic recovery properties, such that the radial extensionof the struts is caused by at least one of a temperature changeassociated with insertion into the PFO and elastic recovery upon removalof the device from the catheter.
 27. The method of claim 25, wherein theradial extension of the struts is assisted by at least one tensionercomprising at least one of an elastic band and a string, the tensionerattached at one end to a strut extending from the distal end of thetubular structure and at the other end to an opposing strut extendingfrom the proximal end of the tubular structure.
 28. The method of claim25, wherein a tissue scaffold is attached to at least one of the struts.29. The method of claim 25, wherein the tubular device includes acentral structure that assists a healing of a tissue adjacent to the PFOfollowing insertion of the device, the central structure comprising atleast one of whiskers attached to the exterior of the tubular structureand a collar including a drug-dispensing sponge-like material.